Untangling The Cosmos, a conference this week organized by the Canadian Institute For Advanced Research, offered a glimpse of the current state of astronomical theory and observation in Canada. If you had questions about the frustrations of using lunchroom microwaves near ultra-sensitive microwave detecting equipment, or about how a huge balloon launched in Antarctica overcame the limitations of ground-based telescopes, then this was the place to be. Here, the National Post’s Joseph Brean rounds up three of the grandest lingering astronomical mysteries discussed at the gathering.

Black Holes don’t suckEver since the early 1970s, when the theory that matter could collapse to a singularity from which nothing can escape — a black hole — was shown to be not just true but pretty common, there have been many misinterpretations about what black holes actually are, and what they do.

Physically, a black hole is actually quite simple, characterized almost entirely by two basic factors: its mass, and how fast it is spinning. It is an object whose escape velocity (the speed at which something must travel to overcome gravity) is greater than the speed of light. By comparison, Earth’s escape velocity is about 12 kilometres per second.

At a black hole’s centre is a singularity — a point into which matter has been infinitely compressed — and this is surrounded by an event horizon, marking the spherical boundary inside which everything is eternally invisible from outside.

Thanks to their mystical reputation, modern discovery, and baffling nature, black holes have played a major role in speculative science fiction, including as the portals for time travel or warp speed. When the Large Hadron Collider was switched on in Switzerland to seek the Higgs boson particle, there were even fears, promoted by serious people, that it might create a black hole that would swallow up the Earth.

This is a misinterpretation. “Black holes don’t suck,” said Daryl Haggard, a McGill University astrophysicist an expert in black holes. “Black holes are not vacuum cleaners. They do not walk through the galaxy sucking.”

There’s a subtle point here about gravity and how it works. Gravity is attractive, but it is not voracious. Even the way a black hole grows is not by sucking surrounding matter out of an otherwise stable orbit, but by surrounding matter gradually losing its own energy and falling into the black hole.

This point has great relevance for the study of the structure of galaxies, most of which have a huge black hole at their centre. In the Milky Way, for example, that black hole is called Sagittarius A*, and it is four million times the mass of the Sun. Far from gobbling them up, these black holes instead keep galaxies in place.

Haggard illustrated the point with a thought experiment: If you magically replaced the Sun with a black hole of the same mass (which would have an event horizon about 3km across) nothing would change for the orbits of the planets in our solar system. We would all freeze to death quite quickly, of course, but it would not suck the planets into their death.

Everything is made of exploded stars

In the universe, a star explodes about once a second. In our galaxy, it happens about once a century. Lars Bildsten, an astrophysicist from the University of California, Santa Barbara, explained this process and how it has led to the creation of all the elements in the periodic table.

“That’s where they’re being made, in these stars that explode,” he said. He described a star as a giant furnace, in which the basic fuel of hydrogen and helium, the lightest elements, are fused into the heavier ones. The result is like a multi-layered jawbreaker, with an iron core, surrounded by layers of silicon, oxygen, carbon, helium, then a layer of hydrogen and helium.

When stars approach the end of their life and explode as supernovae, they release colossal amounts of light, which makes them pretty easy to notice — you just look at a large swath of the sky today, then subtract the view from yesterday. As they do, the iron core collapses in about a second, setting off a shock wave that takes as much as a day to reach the star’s surface, which is blown apart, sending the newly fused elements out into space.

Bombarded by radio wavesThousands of times each day, the Earth receives a strange signal from outer space, a fast burst of radio waves that lasts only a few thousandths of a second. Even stranger: at least some of them appear to repeat.

“We really don’t know what they are,” said Vicky Kaspi, an astrophysicist, director of the McGill Space Institute, and expert in the science of massive neutron stars.

One “major clue” about the origin of these FRBs, Kaspi said, is in the way they arrive, with a distinctive falling frequency. The higher frequency radio waves arrive first, followed by the lower frequency waves. This is likely to be what is known as a propagation effect, meaning the original event, whatever it is, emits all frequencies at the same time, but over the time it takes for the signal to travel to Earth, the low frequencies are slowed down ever so slightly more than the fast ones. The result is the signature falling signal.

If this is the case, and the radio waves are being ever so slightly slowed during their journey (the leading theory), then they must be very, very far away. It would take a sizeable share of the age of the universe for that effect to show up as clearly as it does in the FRBs that are being detected by radio telescopes today. And if they really are being sent from that far away, and we are still detecting them after all those intervening millions of years of travel through space, then they must have started out as very, very bright.

This is the great interest to science, these major cataclysms that happen all the time across the universe, but remain a mystery. Perhaps they are coming from exploding stars, or colliding neutron stars, or comets smashing into neutron stars, or maybe they are something even more fanciful, like evaporating black holes or “oscillating primordial cosmic strings.”

Comments

We encourage all readers to share their views on our articles and blog posts. We are committed to maintaining a lively but civil forum for discussion, so we ask you to avoid personal attacks, and please keep your comments relevant and respectful. If you encounter a comment that is abusive, click the "X" in the upper right corner of the comment box to report spam or abuse. We are using Facebook commenting. Visit our FAQ page for more information.

Almost Done!

Postmedia wants to improve your reading experience as well as share the best deals and promotions from our advertisers with you. The information below will be used to optimize the content and make ads across the network more relevant to you. You can always change the information you share with us by editing your profile.

By clicking "Create Account", I hearby grant permission to Postmedia to use my account information to create my account.

I also accept and agree to be bound by Postmedia's Terms and Conditions with respect to my use of the Site and I have read and understand Postmedia's Privacy Statement. I consent to the collection, use, maintenance, and disclosure of my information in accordance with the Postmedia's Privacy Policy.

Postmedia wants to improve your reading experience as well as share the best deals and promotions from our advertisers with you. The information below will be used to optimize the content and make ads across the network more relevant to you. You can always change the information you share with us by editing your profile.

By clicking "Create Account", I hearby grant permission to Postmedia to use my account information to create my account.

I also accept and agree to be bound by Postmedia's Terms and Conditions with respect to my use of the Site and I have read and understand Postmedia's Privacy Statement. I consent to the collection, use, maintenance, and disclosure of my information in accordance with the Postmedia's Privacy Policy.